Unable to update AT&T Galaxy S5 on stock Touchwiz to Lollipop

[sidward35]

I have an AT&T Galaxy S5 that has the default version of Touchwiz on it, with Android 4.4.2. I never rooted or flashed any roms on this device, yet I am unable to get OTA updates.

My friend, who has the same phone with AT&T, updated to Lollipop a while ago, and recently got another update, both of which I didn't get. Whenever I check for updates on my phone, under the About Device section in system settings, it says "Software Update Interrupted. No update is available for your device at this time. Please try again in 24 hours."

What can I do to update my device to Lollipop?

Thanks,
Sid